In mining and earthworking operations, it is common to utilize replaceable cutting bits on a power driven wheel such as illustrated in a McKenry and Oaks, U.S. Pat. No. 3,720,273 (1973). It is desirable to be able to place, remove, and replace these bits quickly and easily. Devices for retaining these bits in mounting blocks have included collapsible rings of flexible material. Some of these rings are of the type which are applied to the projecting end of a bit shank after it is installed in a mounting lock as exemplified in a Emmerich U.S. Pat. No. 4,763,956 (1988). Other types include flexible retainers which can be preloaded on a bit shank and which are collapsible as they are pushed through the bore in the bit mount. These preload rings are exemplified in a deMey III U.S. Pat. No. 4,582,364 (1986) and a British patent No. 2,105,768 (published Mar. 30, 1983).
The present invention is directed to a preload type flexible retainer which can be placed on a bit prior to installation and which will retain a bit in the mount until the retainer is removed and the worn bit is replaced. The retainer of the present invention can be utilized on what is referred to as an external application where an end of the bit is exposed. Also, it may be used on an internal bit where the shank is not exposed.
The retainer is used in combination with a bit shank which will receive the retainer in collapsed condition during installation but which is designed to cooperate with the retainer in the mining operation to securely lock the bit in place until intentionally removed.
It is a further feature to provide a structure wherein the retainer can be utilized internally in a mounting block, that is, not exposed but which can be released by a seal plug which functions to protect the shank from detritus but also will serve as a release mechanism.
The objects and features of the invention are achieved by the use of a bit shank having a double diameter groove spaced inwardly from the distal end, the smaller diameter being provided to receive the collapsed retainer during installation and the larger diameter groove providing shoulder support for the expanded retainer when the bit is being used. In one embodiment a closed end tubular plug is located in the end of the opening in the mounting block to enclose that end, and the end of the tubular plug within the opening can, when projected inwardly, contract the retainer to allow removal of the bit. In each case there is a positive lock until the retainer is removed.
Other objects and features of the invention will be apparent in the following description and claims in which the principles of the invention are set forth together with details to enable persons skilled in the art to practice the invention all in connection with the best mode presently contemplated for the invention.